Flood loading on heritage bridges - looking after Low Sizergh Suspension Bridge

Low Sizergh Suspension Bridge has suffered repeated cycles of damage and repair over the last few years due to what was formerly considered “extreme” flooding. This paper asks what the appropriate response is to climate dependent increased loading for heritage protected structures. The relevant design decisions are explored for Low Sizergh Suspension Bridge, referring to the tension between principles of conservation and the professional obligations of a structural engineer to provide a robust and safe solution. Data on flood levels for 50 years is examined, looking at the changes in flooding frequency and hence return period for the most severe floods. Given repeated and increasing flood levels, what action should be taken to protect a 150-year-old footbridge? Given the footbridge does not comply with modern design standards, at what point does a repair to an existing structure need to bring the capacity up to current standards?